The Virgin Islands Water and Power Authority was forced to implement small-scale rotating service interruptions in the St. Thomas – St. John district on Friday and Saturday nights, due to a lack of generation capacity to meet the demand for electric service.
WAPA Chief Executive Officer Julio A. Rhymer, Sr. said the recent generation problems to affect the Authority began on Friday morning, when Unit 15, a 20-megawatt generator, tripped. “The failure of Unit 15 had a domino effect on another generating unit, Unit 18, and with the loss of the units, several feeders fell off line. At the time of the service interruption, both units were dispatched providing more than half of the district’s power demand,” Rhymer said.
He said while plant engineers were able to restore Unit 15 and together with Units 14 and 25, re-energize the affected feeders, the combined power of the three units was not enough to satisfy the peak power demand by the end of the day. As a result, feeders were taken off line as the demand for service grew Friday evening. By late night, demand tapered off and full service was restored. The same scenario played out on Saturday evening, when rotating service interruptions became necessary once demand exceeded generation capacity.
WAPA Chief Operating Officer of the Electric System, Clinton Hedrington, Jr., reported that failed components in Unit 18’s generator section will keep the unit sidelined for a short time. “Engineers and technical personnel must replace components and then thoroughly inspect the unit before we attempt to bring it back on line,” he said. Without Unit 18 and the largest generator, Unit 23, the remaining three units (14, 15 and 25) produced an approximate 51megawatts of electricity, short of the capacity required to meet peak demand. Unit 23 had been off line for temporary maintenance ahead of its major overhaul later this year. While attempts were unsuccessful on both Friday night and Saturday to bring Unit 23 on line, the unit was successfully restarted and brought into service Sunday afternoon. Hedrington said Unit 23 was dispatched once problems in the excitation section of the generating unit were addressed.
With Unit 23 online, along with Units 15 and 25, Hedrington said generation capacity was adequate on Sunday night, negating the need to engage a rotating service interruption schedule.
Rhymer said the plant’s technical staff are also working to pinpoint what caused the initial trip on Unit 15.